This invention relates to a power-supply circuit comprising a power-storage means for storing the power supplied by an a.c. source in specific time intervals in which the alternating voltage source is connected to said power-storage means, comprising a switch for taking power from the power storage means, and comprising a control circuit for periodically actuating the switch.
The book "Schaltnetzteile in der Praxis" by Otmar Kilgenstein, Vogel Buchverlag, pages 105 ff. describes a forward converter for mains operation in which the mains voltage is rectified in a rectifier bridge and charges a storage capacitor. The storage capacitor is connected to the series arrangement of the primary winding of a transformer and a transistor, which transistor is alternately turned on and off by a control circuit. The power can be taken from the storage capacitor via a secondary winding of the transformer.
In the known circuit arrangement the switching operations of the periodically actuated switching transistor give rise to undesired high-frequency voltages and currents on the a.c. source, i.e. for example on the a.c. mains, which may give rise to interference in, for example, further loads powered by the alternating voltage source. In order to suppress such interference it is known to arrange passive high-frequency filters comprising coils, capacitors and, if required, resistors between the a.c. source and the other sections of the other circuit arrangement. Such an interference filter is mentioned in "Schaltnetzteile in der Praxis" in the caption to FIG. 5.1 on page 105. However, such filters are complex and expensive, and they also occupy a substantial part of the total circuit volume.